1. Field of the Invention
The present invention pertains to quick disconnect couplers operatively inter-connected with a cryogenic liquid fluid transfer apparatus and associated with a cryogenic fluid storage vessel. Specifically, the invention pertains to the use of a laterally severed tubular bushing that serves to inhibit ice formation, at a coupler inlet/male nipple interface during liquid fluid transfer. In addition, a vent fitting, having one end attached to radial aperture in a coupling sleeve inlet portion, and another end in operative connection with the cryogenic storage vessel, permits inlet purging by using the vessel's own gaseous phase as a purging medium during the liquid fluid transfer operation.
Quick disconnect couplers are well known and are utilized in every conceivable type of fluid transfer application. One of the intended types of end products utilizing the quick disconnect cryogenic coupler of the present invention are portable liquid oxygen units. Such units, in one application, are typically used by patients suffering from Chronic Obstructive Pulmonary Disease (COPD) and provide them with oxygen. In such an apparatus, liquid oxygen, stored in a small cryogenic dewer, is converted to breathable gas, via a warming mechanism, thereby providing the patient with warmed O2 at a given pressure and flow rate. For such applications, the portable cryogenic dewers are filled from larger stationary refill tanks, with the cryogenic coupler of this invention being utilized in such cryogenic liquid fluid transfer apparatuses. It should be understood that cryogenic couplers are also utilized in other cryogenic applications, not just at the end product, but also at the end of fluid transfer apparatuses, such as hoses, tubing or ducting, and with Liquid Natural Gs (LNG) couplings and the like.
In terms of the operation, the male half of the coupling, namely the nipple, is inserted into the female half of the coupling, namely the coupler. Internal valves in both halves are opened as the coupler and nipple are united, with a complete coupling connection therebetween constituting the “coupling”. Once both internal valves are open, liquid fluid is allowed to flow from the nipple into and through the coupler. Once the desired amount of fluid has passed through the coupling, the two halves are pulled apart, with this disconnection process also allowing the two internal valves to shut, thereby preventing any further fluid transfer through the coupler.
Cryogenic fluid transfer, due in large part to the great difference in the ambient temperature and that of the fluid being transferred, involves icing, due mainly to condensation, particularly at the nipple/coupler interface. One known method of reducing such icing is to utilize a thermal break angle, between the nipple and coupler, by incorporating, in the sleeve of the coupler, of an about 10 degree change in its inlet diameter, thereby allowing a thermal break during the noted refill process. Such a construction allows an air break between the coupler and the nipple, thus preventing ice from freezing the two halves together.
Another known way for reducing ice formation between the two coupling halves is the use of a purge mechanism, such as a purging medium, e.g., an external purge gas, such as compressed air. Such purging does remove moisture but requires an additional, external supply of a purging medium.
2. Description of the Related Art
The patent literature sets forth a large number of cryogenic coupling constructions, some of which include: U.S. Pat. No. 3,842,614 to Karcher et al.; U.S. Pat. No. 5,265,844 to Westfall; U.S. Pat. No. 5,363,879 to Rhoades; U.S. Pat. No. 5,429,155 to Brzyski et al.: U.S. Pat. No. 5,880,043 to Lorenz et al.; U.S. Pat. No. 6,047,553 to Germain; U.S. Pat. No. 6,079,446 to Tocha; U.S. Pat. No. 6,145,322 to Odajima; and U.S. Pat. No. 6,539,970 B1 to Knowles et al. However, none of these prior art structures include the use of a laterally severed tubular bushing that functions as an anti-freezing lining inside the coupler, relative to the adjoining nipple portion. In addition, all of the prior art structures utilize an external source for a purge medium, not the purging gas emanating from the unit being charged or refilled with the liquid phase of the purging gas.